1. Field of the Invention
The present invention relates to electrical connectors. More specifically, the present invention relates to high density edge card connectors.
2. Brief Description of Earlier Developments
Edge card connectors have been used for a substantial period of time. As with many other connector types, there has been a continual evolution of these connectors in terms of size reduction, terminal pitch, and electrical performance. In order to reduce the size of the connector and in many cases increase the signal density, it is necessary to decrease the terminal pitch.
The decrease in terminal pitch necessitates a decrease in the amount of insulative material between terminals, thereby resulting in very thin walls between terminals. The insertion of terminals into the terminal cavities can result in rupturing these thin walls between terminal cavities. Also an accumulation of stress along the lengthwise dimension of the connector can occur. However, the decreased wall thicknesses in the connector housing render the housing less able to resist the stress accumulation. As a result, the connector tends to bow. This adversely affects conformance of the connector to the circuit board on which it is mounted and creates alignment difficulties, particularly in surface mount connectors, with contact pads on the printed circuit board.
In addition, many prior designs employ relatively long length contact arms in order to develop sufficient deflection to accommodate daughter board thickness tolerances and to obtain good contact normal forces between the contacts and the terminals of the connector. This increases the impedance of the connector and can unduly increase skew.
It is an object of the present invention to minimize the accumulation of stresses in the connector housing.
It is a further object of the present invention to employ relatively light retention forces when inserting terminals into the housing.
It is a further object of the present invention to utilize an element secured to the housing after terminal insertion to hold the terminals in place within the housing.
It is a further object of the present invention to provide terminals having features to help retain the terminal within the insulative housing during handling.
It is a further object of the present invention to provide terminals that are movable with respect to the housing to accommodate differences in the coefficient of thermal expansion (CTE) of the connector body and the printed circuit board upon which the connector mounts.
It is a further object of the present invention to employ deformable elements, such as solder balls, to secure the terminals to the housing.
It is a further object of the present invention to provide a connector that can be closely stacked in an end-to-end configuration with another connector.
These and other objects of the present invention are achieved in one aspect of the present invention by an electrical connector comprising: an insulative housing having at least one cavity; a retaining member removably securable to the insulative housing and occluding at least a portion of the cavity, the retaining member having at least one aperture in communication with the cavity; a conductive terminal having a first portion disposed in the cavity and a second portion disposed in the aperture; and a surface mount element mounted on the second portion of the terminal. The member retains the terminal within the insulative housing.
These and other objects of the present invention are achieved in another aspect of the present invention by a card edge connector, comprising: an insulative housing, a conductive terminal, a retaining member and a surface mount element. The insulative housing has: a slot for receiving an edge of a card; a cavity in communication with the slot and a pair of posts, each having channels in communication with the slot for receiving the card. The conductive terminal has a mating portion residing within the cavity for engaging the card edge and a mounting portion extending from the cavity. The retaining member secures to the insulative housing and has an aperture in communication with the cavity that receives the mounting portion of the terminal. The retaining member preventing the terminal from exiting the cavity. The surface mount element attaches to the mounting portion of the terminal.
These and other objects of the present invention are achieved in another aspect of the present invention by a method of making an electrical connector, comprising the steps of: providing an insulative housing having a cavity; providing a conductive terminal having a mounting portion; providing a retaining member having an aperture; providing a surface mount element; inserting the terminal into the cavity; attaching the retaining member to the insulative housing, wherein the mounting portion of the terminal resides within the aperture; and securing the surface mount element to the mounting portion of the terminal. The retaining member keeps the terminal within the cavity.